The focus of this project is to identify genes that are important in the normal development of the inner ear using the chick as a model. The inner ear undergoes elaborate morphological changes during development. Perturbation of this developmental process very often leads to functional deficits. A good knowledge of the molecular basis that underlies the morphological events occurring during normal inner ear development will facilitate the understanding of genetic defects which result in functional deficits. Three members of the tumor growth factor beta (TGFbeta) gene family, bone morphogenetic protein (BMP) 4, 5 and 7, which were expressed during early otocyst development have been identified to date. The onset of expression is different for each of the BMPs during otocyst development. However, by embryonic day 2.5, the developmental age at which the otocyst is formed, the expression of all BMPs starts to become restricted to the future ampullae of the otocyst. Since BMPs are expressed in the sensory part of the otocysts prior to any sign of sensory differentiation, these results suggest that the decision to become sensory versus non-sensory structures in the inner ear may be an early developmental event.